Exploratory Study of Aerosol Inhalation of FB2001 for Post-exposure Prophylaxis of COVID-19 Close Contacts

"Stage 1 (Exploring the dose): Twenty participants will be enrolled for aerosol inhalation of FB2001 once daily for 5 consecutive days. If the drug is well tolerated but efficacy is inadequate, another twenty participants will be enrolled for aerosol inhalation of FB2001 BID for 5 consecutive days.~Stage 2 (Sample size expansion): Another twenty participants will be enrolled for aerosol inhalation of FB2001 once daily or twice daily for 5 consecutive days depending on the result of stage 1."